617
FXUS63 KMQT 171917
AFDMQT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
217 PM EST TUE DEC 17 2024
KEY MESSAGES
- LAKE EFFECT SNOW PICKS UP AND COULD BECOME MODERATE AT TIMES
TONIGHT INTO WEDNESDAY NIGHT OVER THE WEST-NORTHWEST, THEN NORTHWEST
WIND SNOW BELTS.
- WINTER WEATHER ADVISORIES ARE IN EFFECT FOR PORTIONS OF THE
WESTERN AND EASTERN UP FOR LAKE EFFECT SNOW LATE TONIGHT INTO
WEDNESDAY NIGHT.
- EYES ARE ON A FAST-HITTING CLIPPER SYSTEM THAT COULD BRING SOME
FLUFFY SNOWFALL OVER THE U.P. THURSDAY AND THURSDAY NIGHT. HOWEVER,
WE MAY MISS OUT ON THE SYSTEM SNOWFALL ENTIRELY SHOULD IT GO TOO FAR
SOUTH. CHANCES TO OF OVER 6"+ OF SNOWFALL ALONG THE MI/WI STATE LINE
HAVE FALLEN TO 10-30%.
SHORT TERM /THROUGH TONIGHT/
ISSUED AT 216 PM EST TUE DEC 17 2024
AFTERNOON WATER VAPOR IMAGERY AND RAP ANALYSES SHOW MIDLEVEL
TROUGHING EXTENDING FROM QUEBEC TO THE LOWER GREAT LAKES, WITH
ANOTHER SHORTWAVE MOVING THROUGH THE PLAINS AND A CLIPPER OVER
MANITOBA. BEHIND THE COLD FRONT ASSOCIATED WITH THE SYSTEM TO OUR
EAST, 850MB TEMPERATURES ARE FALLING TO AROUND -10C ALREADY. THIS
HAS BEEN ENOUGH TO KICK UP SOME WNW LAKE EFFECT SNOW BANDS -
PROMINENT ON RADAR ACROSS THE NORTH-CENTRAL AND EASTERN UP AND
SOMEWHAT OBSCURED ON SATELLITE AS HIGH CLOUD COVER ASSOCIATED WITH
THE PLAINS SYSTEM STREAMS INTO THE AREA. STILL, AT LEAST SOME SPOTTY
LES CAN BE EXPECTED TO THE WEST, WITH OCCASIONAL SURFACE
OBSERVATIONS AND GLIMPSES OF SNOW SHOWERS ON WEBCAMS. SOME LIGHT
ACCUMULATIONS MAINLY BELOW AN INCH ARE POSSIBLE BY 00Z IN THE
EASTERN UP, WITH MAINLY TRACE AMOUNTS TO THE WEST.
OTHERWISE, WNW WINDS REMAIN BREEZY THROUGHOUT THE KEWEENAW, GUSTING
TO 20-30MPH. WINDS SHOULD CONTINUE TO FALL BACK THE REST OF THE DAY,
HOWEVER, WHILE TEMPERATURES HOVER IN THE 20S (WEST) TO LOWER 30S)
EAST) UNDER CLOUDY SKIES.
WEST-NORTHWEST LAKE EFFECT SNOW WILL RAMP UP LATER TONIGHT AS THE
CLIPPER SHORTWAVE TROUGH MOVING THROUGH THE AREA PROVIDES DEEPER
MOISTURE AND MODEST LIFT FOR ENHANCEMENT. THE COMBINATION OF WEAK
LIFT, DEEPER MOISTURE AND CAA WITH 850 MB TEMPS DROPPING TO -12C TO -
13C BY 12Z WED SHOULD LEAD TO 1-3 INCHES OF LES ACCUMULATION TONIGHT
OVER THE WNW SNOW BELTS, GREATEST OVER THE HIGHER TERRAIN OF THE
COPPER COUNTRY, PARTICULARLY FROM IRONWOOD NORTHEAST TO PAINESDALE.
LES CONTINUES THE REST OF WEDNESDAY INTO WEDNESDAY NIGHT, WITH
CHANCES FOR HEAVIER SNOWFALL RATES AROUND/IN EXCESS OF AN INCH PER
HOUR. WITH A POTENTIAL FOR SEVERAL INCHES OF FLUFFY SNOW
ACCUMULATIONS TONIGHT INTO WEDNESDAY NIGHT, A WINTER WEATHER
ADVISORY HAS BEEN ISSUED FOR PORTIONS OF THE WESTERN AND EASTERN UP.
EXPECT LOWS TONIGHT RANGING FROM THE UPPER TEENS TO MID 20S, COOLEST
OVER THE WESTERN INTERIOR AND WARMEST SOUTH CENTRAL AND EAST.
LONG TERM /WEDNESDAY THROUGH MONDAY/
ISSUED AT 419 AM EST TUE DEC 17 2024
A PROGRESSIVE PATTERN CONTINUES OVER THE UPPER GREAT LAKES BEGINNING
WEDNESDAY MORNING AS 500MB TROUGHING SWEEPS OVER THE UP. FOLLOWING
RIDGING WILL BE SHORT-LIVED AS A DIGGING CLIPPER TROUGH RACES
FROM MONTANA TO THE CHICAGO METRO FROM WEDNESDAY NIGHT TO
THURSDAY NIGHT. MORE PROLONGED RIDGING THEN DOMINATES THE
CENTRAL CONUS BEFORE THE NEXT TROUGH IS SET TO ARRIVE OVER THE
GENERAL UPPER MIDWEST REGION TO KICK OFF CHRISTMAS WEEK.
MULTIPLE CHANCES OF SYNOPTIC SNOWFALL ARE POSSIBLE WITH THE
RESULTANT SURFACE FEATURES OF THE AFOREMENTIONED TROUGHS, WITH
THE COLD AIR ALOFT IN THE WAKE OF THOSE TROUGHS PROVIDING LAKE
EFFECT SNOW CHANCES. TEMPERATURES THROUGH THIS PERIOD WILL
PRIMARILY BE BELOW NORMAL FOR THIS TIME PERIOD, AND WITH
MULTIPLE DIFFERENT MECHANISMS FOR SNOWFALL, A "WHITE CHRISTMAS"
REMAINS POSSIBLE, THOUGH A WARMUP IN THE BEGINNING OF CHRISTMAS
WEEK KEEPS THAT SOLUTION SOMEWHAT UNCERTAIN.
AS HAS FREQUENTLY BEEN THE CASE THIS WINTER SO FAR, NORTHWESTERLY
LAKE EFFECT SNOW WILL BE ONGOING WEDNESDAY MORNING. SLIGHTLY
CYCLONIC SURFACE-LAYER FLOW WILL PROVIDE SOME CONVERGENCE TO SUPPORT
THE BANDS, AND THE THERMODYNAMIC SUPPORT IS DEFINITELY PRESENT WITH
850MB TEMPERATURES FALLING TO NEAR -20 C BY 21Z WEDNESDAY PER THE
00Z GFS. THIS CONTRASTED WITH LAKE SUPERIOR TEMPERATURES OF AROUND 6
C WILL PROVIDE GOOD DELTA TS, THOUGH SOUNDINGS SHOW SATURATION NEAR
TO THE TOP OF THE DGZ OR ABOVE WITH SIGNIFICANT DRY AIR AT AND ABOVE
THE INVERSION, SO QPF WILL BE LIMITED. 00Z HREF SHOWS ONLY A 10%
CHANCE OF 1"/HR SNOWFALL RATES IN THESE BANDS, AND WITH 6-HOURLY PMM
SNOWFALL RATES PEAKING AT AROUND 0.1"/6HR, SNOWFALL RATES WILL ONLY
RARELY EXCEED "LIGHT-TO-MODERATE" RANGE. BROADLY EXPECTING AROUND 1-
3 INCHES OF FLUFFY SNOWFALL IN THE ALGER/N. SCHOOLCRAFT/LUCE RANGE
AND IN THE HIGH TERRAIN OF THE WEST HALF WITH LESS THAN AN INCH
EXPECTED ELSEWHERE BY THURSDAY MORNING. WIND GUSTS OF 20-30 MPH
COULD CREATE ISOLATED BLOWING AND DRIFTING SNOW ALONG THE SHORELINES
OF LAKE SUPERIOR, BUT WIDESPREAD TRAVEL IMPACTS ARE NOT EXPECTED.
LES INTENSITY AND COVERAGE WILL WANE OVERNIGHT INTO THURSDAY AS
~1030MB HIGH PRESSURE MOVES NEARLY DIRECTLY OVER LAKE SUPERIOR,
PROVIDING SUPPRESSIVE SUBSIDENCE, THOUGH THERMODYNAMICS ALONE WILL
AT LEAST KEEP VERY LIGHT SNOW SHOWERS OVER THE EAST HALF INTO
THURSDAY MORNING. ATTENTION THEN TURNS UPSTREAM TO A FAST-HITTING
CLIPPER LOW OVER THE DAKOTAS 12Z THURSDAY. ENSEMBLES CONTINUE TO
STRUGGLE TO CONGREGATE ON A TRACK, BUT SOME CONSOLIDATION AROUND THE
LOW BEING OVER IL TO SOUTHERN WI BY FRIDAY 06Z IS SEEN IN THE 00Z
GEFS AND EPS (THOUGH THE EPS IS MAYBE 50 MILES FASTER IN THE TRACK),
THOUGH THE CANADIAN ENSEMBLE STILL HAS A NUMBER OF MEMBERS PASSING
THROUGH THE GREEN BAY TO MILWAUKEE AREA. A CLOSER LOW PASSAGE WOULD
PROVIDE SIGNIFICANT FORCING FOR SNOWFALL WITH ISENTROPIC ASCENT AND
WARM ADVECTION AHEAD OF THE LOW ITSELF ACCOMPANIED BY A DGZ AS DEEP
AS 7KFT BY LATE THURSDAY EVENING PER SOUNDINGS. HOWEVER, WITH
ENSEMBLES SEEMINGLY PREFERRING A SOUTHERLY TRACK, CONFIDENCE IN
SNOWFALL OF SIGNIFICANCE (OR AT LEAST, WINTER STORM WARNING
CRITERIA) IS WANING (10-30%, DOWN FROM NEAR 50% FROM PRIOR
FORECASTS). STILL, COMMUNITIES ESPECIALLY ALONG THE MI/WI STATE
LINE THAT HAVE NOT SEEN MUCH SNOW THIS YEAR (THANKS TO BEING
SHELTERED FROM THE NWERLY LES THAT HAS DOMINATED THUS FAR)
SHOULD CONTINUE TO MONITOR THE FORECAST IN CASE TRENDS REVERSE
FOR THURSDAY THROUGH THURSDAY NIGHT.
WHILE LAKE-850MB DELTA TS REMAIN QUITE SUPPORTIVE OF LES IN THE WAKE
OF THE CLIPPER LOW/PARENT TROUGH, HIGH PRESSURE OF UPPER 1030S TO
LOWER 1040S MB APPROACHES THE UP AREA THROUGHOUT FRIDAY AND THE
WEEKEND, REDUCING CONFIDENCE IN ACCUMULATING SNOWFALL, THOUGH
SOME POPS HAVE BEEN KEPT IN THE FORECAST TO ACCOUNT FOR ENSEMBLE
SPREAD. AS THIS HIGH SHIFTS TOWARDS THE LOWER GREAT LAKES LATE
IN THE WEEKEND TO EARLY MONDAY, ATTENTION TURNS UPSTREAM ONCE
AGAIN TO ANOTHER POTENTIAL CLIPPER LOW, THOUGH ONLY CERTAIN
CLUSTERS WITHIN THE ENSEMBLES SHOW THIS SOLUTION, SO POPS ARE
ONLY AROUND 15-35% TO KICK OFF CHRISTMAS WEEK AT THIS TIME. A
MORE ZONAL PATTERN AROUND THIS TIME HAS THE NBM HIGHS CLIMBING
BACK TOWARDS FREEZING AROUND THIS TIME, WHICH COULD COMPLICATE
THE WHITE CHRISTMAS FORECAST SOMEWHAT, BUT WITH MULTIPLE
MECHANISMS FOR SNOW AND PLENTY OF COOL AIR THIS WEEK (LOWS
FREQUENTLY IN THE SINGLE DIGITS FOR MUCH OF THE INTERIOR UP), IT
MIGHT TAKE A SIGNIFICANT WARM SWING TO CAUSE A SIGNIFICANT
THREAT TO A WHITE CHRISTMAS.
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 1216 PM EST TUE DEC 17 2024
MVFR CONDITIONS WILL DOMINATE FOR THIS FORECAST PERIOD AT ALL SITES.
SOME BRIEF PERIODS OF IFR CONDITIONS ARE POSSIBLE IN SNOW SHOWERS
OVERNIGHT AS A COLD FRONT PASSES OVER THE UP, THEN IFR SETTLES IN
DURING THE EARLY MORNING HOURS AT IWD AND CMX IN LINGERING LAKE
EFFECT SNOW SHOWERS.
OTHERWISE, WEST WINDS REMAIN BREEZY THIS AFTERNOON, GUSTING TO
AROUND 20 TO 25 KNOTS BEFORE FALLING BACK INTO THE EVENING HOURS.
MARINE
ISSUED AT 419 AM EST TUE DEC 17 2024
ONGOING WESTERLY GALES TO 40 KT WILL WEAKEN IN THE WEST HALF THROUGH
THIS MORNING AND FALL BELOW GALES IN THE EAST BY EARLY AFTERNOON.
WEST-NORTHWEST GUSTS SHARPLY FALL BELOW 20 KT THIS EVENING
THROUGH TONIGHT BEFORE REINVIGORATING TO NORTHWESTERLY GUSTS TO
20-30 KT WEDNESDAY (GALE CHANCES 20% OR LESS). WINDS ONCE AGAIN
FALL BELOW 20 KT IN THE OVERNIGHT PERIOD BEFORE WINDS BEGIN TO
RAMP UP THURSDAY AFTERNOON IN RESPONSE TO A CLIPPER LOW PRESSURE
SYSTEM PASSING SOUTH OF LAKE SUPERIOR. DEPENDING ON HOW CLOSE
THIS SYSTEM PASSES TO THE LAKE, A FEW NORTHEASTERLY GALE FORCE
GUSTS ARE POSSIBLE (20%) IN THE WEST OVERNIGHT THURSDAY, BUT
OTHERWISE, WIND GUSTS CLOSER TO 25 KT ARE MORE LIKELY (~50%). AS
WINDS SWING NORTHWESTERLY, WINDS ONCE AGAIN FALL BELOW 20 KT AS
HIGH PRESSURE DOMINATES THE FORECAST THROUGH THE WEEKEND. THE
WEATHER FOR CHRISTMAS WEEK IS STILL UNCERTAIN, BUT SOME
INDICATIONS OF ANOTHER CLIPPER LOW IN THE MONDAY AFTERNOON-
TUESDAY TIME FRAME PROVIDE CHANCES (~40%) OF WINDS INCREASING
BACK TO 20-30 KT, BUT CONFIDENCE IN THE DETAILS IS LOW AT THIS
TIME.
MQT WATCHES/WARNINGS/ADVISORIES
UPPER MICHIGAN...
WINTER WEATHER ADVISORY FROM 1 AM EST /MIDNIGHT CST/ TO 7 PM
EST /6 PM CST/ WEDNESDAY FOR MIZ002-003-009.
WINTER WEATHER ADVISORY FROM 1 AM WEDNESDAY TO 1 AM EST
THURSDAY FOR MIZ006-007-085.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
SHORT TERM...LC
LONG TERM...GS
AVIATION...LC
MARINE...GS
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